1. Field of the Invention
This invention relates to silicon nitride sintered body of high toughness. This silicon nitride sintered body of high toughness can be utilized as component members of engines such as gas turbine engines, reciprocating engines, diesel engines, and the like. Further, the silicon nitride sintered body of high toughness can be utilized as a material for turbine rotors for superchargers.
2. Description of the Prior Art
As described in Yogyo-Kyokai-Shi (The Ceramic Industry Association Magazine) vol. 91, published in November, 1983, a process has been known to improve mechanical strength of silicon nitride sintered body, in which silicon carbide whiskers are mixed into silicon nitride powder, the mixture is molded and then hot-pressed.
Because the above-mentioned conventional process utilizes the silicon carbide whiskers as fibers for reinforcing the silicon nitride matrix, the conventional process produces one of fiber reinforced ceramics which have been known already by mixing the silicon nitride with the silicon carbide whiskers and then by molding and sintering the mixture. In this fiber reinforced ceramic, only the good mechanical strength of the silicon carbide whisker is utilized, and the silicon nitride as the matrix is utilized as it is, but the silicon nitride itself is not modified at all.